1. Field
This disclosure relates to a superconducting cable device, and more particularly, to a superconducting cable device which is lengthened by connecting a plurality of superconducting cables.
2. Description of the Related Art
In order to maximize an electricity transmission efficiency, a superconducting cable of which the electrical resistance is very low has been developed. The superconducting cable generally includes a cable core made of a superconducting wire of which the electrical resistance is close to 0, and a double heat-insulating pipe which covers the cable core. In order to maintain the cable core which is the superconducting wire in a cooled state at its critical temperature or below, the superconducting cable has a special heat-insulating structure.
Recently, for commercialization of the superconducting cable, an effort to connect a plurality of superconducting cables so as to be lengthened has been made.
To lengthen the superconducting cable, an intermediate connection box capable of connecting the superconducting cables is used. The intermediate connection box functions as a fixed point of the superconducting cables, and inside the intermediate connection box, the superconducting cables are connected.
In order to connect the superconducting cables to each other, the cable cores of the superconducting cables that extend to the inside of the intermediate connection box are fixed to each other by soldering. In order to firmly maintain the fixed state of the connected cable cores, the connected cable cores are taped and fixed using insulating paper for superconducting cables such as polypropylene laminated paper (PPLP). Accordingly, a thick cable connection portion is formed inside the intermediate connection box.
In order to ensure the performance of the superconducting cable device which is lengthened, the position of the cable connection portion inside the intermediate connection box needs to be optimized. If the position of the cable connection portion is not optimized, for example, insulation breakdown of the cable connection portion may occur due to heat that locally invades the intermediate connection box. In addition, as the position of the cable connection portion is moved due to heat shrinkage of the superconducting cable during a cooling process, the cable connection portion comes in contact with an inner box of the intermediate connection box and is damaged.